The prior art related to ear plugs includes the following United States patents.
U.S. Pat. No. 2,053,995 to Hoey shows a device with a threaded shaft which can be rotated using the projections formed on an inner shaft to expand a hollow body. The hollow body is expanded to create a seal against the ear canal when the device is shortened using a threaded shaft which is attached to the end of the hollow body.
U.S. Pat. No. 2,888,921 to Nielson et al. shows a balloon-like member which fills the ear canal. The balloon-like member is pressurized slightly above normal atmospheric pressure and a tubular member aids in the insertion of the balloon-like member into the ear. The internal pressure in the balloon-like member creates a seal against the ear canal.
U.S. Pat. No. 3,783,864 to Moller shows a flexible member which can be expanded to fit the ear canal by rotation of a nut. The device includes a hollow tube for transmission of sound.
U.S. Pat. No. 3,123,069 to Laisne et al. shows a plunger which acts to change the diameter of a hollow member to allow insertion and to provide a close fit in the ear canal. The plunger is attached to the end of the hollow member. The plunger serves to elongate the hollow member thereby reducing the diameter for insertion into the ear canal.
U.S. Pat. No. 3,800,791 to Visor shows a device in which a threaded insert is rotated and is thereby forced into a cavity in an ear plug resulting in the increase in the diameter of a flexible flange to create a seal in the ear canal.
U.S. Pat. No. 6,830,124 B2 and 2004/0211621 A1 to Chaing shows a device which incorporates an integral handle for insertion and removal of the device. The device relies on the flexibility of flange-like members to create a seal.
Despite the various developments in the prior art, there remains a need for an ear
plug with an adjustable shaft which combines ease of use with a high degree of retention in the user's ear with effective sealing against entry of water into the user's ear canal.